Apparatus, methods, computer programs and non-transitory computer readable storage mediums for machining objects

ABSTRACT

Apparatus for machining an object, the apparatus comprising: a wheel including; a first circular surface; a second circular surface oriented parallel to the first circular surface; a first rim surface extending from the first circular surface at a first edge, a gradient of the first rim surface having a radial component; and a second rim surface extending from the second circular surface at a second edge and towards the first rim surface, a gradient of the second rim surface having a radial component, the first edge defining a curved surface between the first circular surface and the first rim surface, and the second edge defining a curved surface between the second circular surface and the second rim surface.

TECHNOLOGICAL FIELD

The present disclosure concerns apparatus, methods, computer programs,and non-transitory computer readable storage mediums for machiningobjects

BACKGROUND

Contact wheels may be used to machine objects such as fan blades of gasturbine engines. For example, a contact wheel may be used in conjunctionwith an abrasive belt to linish a wide chord fan blade (WCFB) to removea surface layer that is formed during a preceding hot superplasticforming (SPF) process.

Contact wheels have flat circumferential surfaces which may be unable toaccess concave features of an object (such as the root fillet of a fanblade). Currently, an operator may handle the machining apparatus tomanually move the contact wheel against the object to machine suchfeatures on the object. However, such manual handling of the machiningapparatus may present health and safety risks. For example, machining afan blade of a gas turbine engine may produce titanium dust which is afire hazard. Furthermore, manually handling the machining apparatus maycause an industrial injury such as hand-arm vibration syndrome (HAVS)(also known as vibration white finger (VWF)).

BRIEF SUMMARY

According to various, but not necessarily all, examples there isprovided apparatus for machining an object, the apparatus comprising: awheel having a circumference, the wheel including: a first circularsurface; a second circular surface oriented parallel to the firstcircular surface; a first rim surface extending from the first circularsurface at a first edge and defining at least a part of thecircumference of the wheel, a gradient of the first rim surface having aradial component; and a second rim surface extending from the secondcircular surface at a second edge and towards the first rim surface, thesecond rim surface defining at least a part of the circumference of thewheel, a gradient of the second rim surface having a radial component,the first edge defining a curved surface between the first circularsurface and the first rim surface, and the second edge defining a curvedsurface between the second circular surface and the second rim surface.

According to various, but not necessarily all, examples there isprovided apparatus for machining an object, the apparatus comprising: awheel having a circumference, the wheel including: a first circularsurface; a second circular surface oriented parallel to the firstcircular surface; a first rim surface extending from the first circularsurface at a first edge and defining at least a part of thecircumference of the wheel, a gradient of the first rim surface having aradial component; and a second rim surface extending from the secondcircular surface at a second edge and towards the first rim surface, thesecond rim surface defining at least a part of the circumference of thewheel, a gradient of the second rim surface having a radial component,the first edge defining a curved surface between the first circularsurface and the first rim surface. The first rim surface and the secondrim surface may be directly joined to one another with no interveningsurfaces there between.

The first rim surface and the second rim surface may abut one another ata location equidistant between the first circular surface and the secondcircular surface.

The first rim surface, the second rim surface, the first edge and thesecond edge may be arranged to receive an abrasive belt for linishingthe object.

The first rim surface, the second rim surface, the first edge and thesecond edge may comprise an abrasive material for polishing or grindingthe object.

The first rim surface, the second rim surface, the first edge and thesecond edge may define a plurality of grooves.

The object may include a filleted part extending along a longitudinalaxis. The apparatus may further comprise a controller configured tocontrol orientation of the wheel and/or the object so that a cylindricalaxis of the wheel is orthogonal to the longitudinal axis of the filletedpart during machining of the object.

The wheel may include a hub comprising aluminium and a perimeter sectioncomprising rubber.

According to various, but not necessarily all, examples there isprovided a method of controlling apparatus as described in any of thepreceding paragraphs to machine an object including a filleted partextending along a longitudinal axis, the method comprising: controllingorientation of the wheel and/or the object so that a cylindrical axis ofthe wheel is orthogonal to the longitudinal axis of the filleted partduring machining of the object.

According to various, but not necessarily all, examples there isprovided a computer program that, when read by a computer, causesperformance of the method as described in any of the precedingparagraphs.

According to various, but not necessarily all, examples there isprovided a non-transitory computer readable storage medium comprisingcomputer readable instructions that, when read by a computer, causeperformance of the method as described in any of the precedingparagraphs.

According to various, but not necessarily all, examples there isprovided apparatus for controlling machining of an object, the apparatuscomprising: a controller configured to perform a method as described inany of the preceding paragraphs.

The skilled person will appreciate that except where mutually exclusive,a feature described in relation to any one of the above aspects may beapplied mutatis mutandis to any other aspect. Furthermore except wheremutually exclusive any feature described herein may be applied to anyaspect and/or combined with any other feature described herein.

BRIEF DESCRIPTION

Embodiments will now be described by way of example only, with referenceto the Figures, in which:

FIG. 1 illustrates a schematic diagram of an apparatus for machining anobject according to various examples;

FIG. 2 illustrates a cross sectional diagram of a wheel according tovarious examples;

FIG. 3 illustrates a perspective view of another wheel according tovarious examples;

FIG. 4 illustrates a flow diagram of a method of machining an objectaccording to various examples;

FIG. 5 illustrates a perspective view of a fan blade to be machined by awheel according to various examples;

FIG. 6 illustrates a schematic diagram of the fan blade illustrated inFIG. 5 being machined by a wheel according to various examples;

FIG. 7 illustrates a graph of pressure applied by two different wheelsalong a radial length of a concave surface of the fan blade illustratedin FIGS. 5 and 6 according to various examples; and

FIG. 8 illustrates a perspective view of the fan blade illustrated inFIGS. 5 and 6 and the distribution of pressure applied by the wheelaccording to various examples.

DETAILED DESCRIPTION

In the following description, the terms ‘connected’ and ‘coupled’ meanoperationally connected and coupled. It should be appreciated that theremay be any number of intervening components between the mentionedfeatures, including no intervening components.

FIG. 1 illustrates a schematic diagram of an apparatus 10 for machiningan object 12. The apparatus 10 includes a controller 14, one or moreactuators 16, one or more sensors 18, and a wheel 20. In some examples,the apparatus 10 may be a module. As used herein, the wording ‘module’refers to a device or apparatus where one or more features are includedat a later time, and possibly, by another manufacturer or by an enduser. For example, where the apparatus 10 is a module, the apparatus 10may only include the wheel 20, and the remaining features (such as thecontroller 14, the actuators 16, and the sensors 18) may be added byanother manufacturer, or by an end user. By way of another example,where the apparatus 10 is a module, the apparatus 10 may only includethe controller 14, and the remaining features (such as the actuators 16,the sensors 18 and the wheel 20) may be added by another manufacturer,or by an end user.

The object 12 may be any object for machining by the apparatus 10 andmay be a component of a gas turbine engine for example. The object 12may comprise one or more concave surfaces for machining by the apparatus10. For example, the object 12 may be a fan blade of a gas turbineengine where the root portion and the aerofoil portion define a filletedpart (having a concave surface) there between. In other examples, theobject 12 may be a turbine blade, a compressor blade, a stator vane, avariable guide vane, or a nozzle guide vane of a gas turbine engine. Infurther examples, the object 12 may be a marine propeller or a propellerfor an aeroplane.

The controller 14, the actuators 16 and the sensors 18 may be coupled toone another via a wireless link and may consequently comprisetransceiver circuitry and one or more antennas. Additionally oralternatively, the controller 14, the actuators 16, and the sensors 18may be coupled to one another via a wired link and may consequentlycomprise interface circuitry (such as a Universal Serial Bus (USB)socket). It should be appreciated that the controller 14, the actuators16 and the sensors 18 may be coupled to one another via any combinationof wired and wireless links.

The controller 14 may comprise any suitable circuitry to causeperformance of the methods described herein and as illustrated in FIG.4. The controller 14 may comprise: at least one application specificintegrated circuit (ASIC); and/or at least one field programmable gatearray (FPGA); and/or single or multi-processor architectures; and/orsequential (Von Neumann)/parallel architectures; and/or at least oneprogrammable logic controller (PLC); and/or at least one microprocessor;and/or at least one microcontroller; and/or a central processing unit(CPU); and/or a graphics processing unit (GPU), to perform the methods.

By way of an example, the controller 14 may comprise at least oneprocessor 22 and at least one memory 24. The memory 24 stores a computerprogram 26 comprising computer readable instructions that, when read bythe processor 22, causes performance of the methods described herein,and as illustrated in FIG. 4. The computer program 26 may be software orfirmware, or may be a combination of software and firmware.

The processor 22 may include at least one microprocessor and maycomprise a single core processor, may comprise multiple processor cores(such as a dual core processor or a quad core processor), or maycomprise a plurality of processors (at least one of which may comprisemultiple processor cores).

The memory 24 may be any suitable non-transitory computer readablestorage medium, data storage device or devices, and may comprise a harddisk and/or solid state memory (such as flash memory). The memory 24 maybe permanent non-removable memory, or may be removable memory (such as auniversal serial bus (USB) flash drive or a secure digital (SD) card).

The computer program 26 may be stored on a non-transitory computerreadable storage medium 28. The computer program 26 may be transferredfrom the non-transitory computer readable storage medium 28 to thememory 24. The non-transitory computer readable storage medium 28 maybe, for example, a USB flash drive, a secure digital (SD) card, acompact disc (CD), a digital versatile disc (DVD) or a Blu-ray disc. Insome examples, the computer program 26 may be transferred to the memory24 via a signal 30 (which may be a wireless signal or a wired signal).

The one or more actuators 16 are configured to position and orient thewheel 20 and/or the object 12. In one example, the actuators 16 mayinclude a first actuator (such as a servo motor) configured to move andorient the wheel 20 relative to the object 12, and a second actuator(such as a motor) configured to rotate the wheel 20 to machine theobject 12. The object 12 may be held in a static position by one or morefixtures. In another example, the actuators 16 may include the first andsecond actuators as described above and may additionally include a thirdactuator (such as a servo motor) configured to move and orient theobject 12 relative to the wheel 20. The controller 14 is configured tocontrol the operation of the one or more actuators 16.

The one or more sensors 18 may comprise any suitable sensors for sensingthe position of the surfaces of the object 12. For example, the one ormore sensors 18 may comprise a contact three dimensional sensor such asa co-ordinate measuring machine (CMM) that is configured to sense theposition of the surfaces of the object 12 using a mechanical probe. Inanother example, the one or more sensors 18 may additional oralternatively comprise a non-contact three dimensional sensor to sensethe position of the surfaces of the object 12 using an acoustic wavesensor (such as an ultrasound sensor) or an electromagnetic wave sensor(such as an optical light sensor). The controller 14 is configured tocontrol the operation of the one or more sensors 18 and is configured toreceive information from the one or more sensors 18.

The wheel 20 is described in greater detail below with reference toFIGS. 2 and 3.

FIG. 2 illustrates a cross sectional diagram of the wheel 20 and acylindrical polar coordinate system 32 according to various examples.The cylindrical polar coordinate system 32 includes a cylindrical axis34 (which may also be referred to as a longitudinal axis 34), a polaraxis 36 and an azimuthal axis 38 (that extends into the page asillustrated in FIG. 2). The cylindrical axis 34, the polar axis 36 andthe azimuthal axis 38 are orthogonal to one another.

The wheel 20 has a circumference 40 and includes: a first circularsurface 42; a second circular surface 44, a first rim surface 46, asecond rim surface 48, a first edge 50 and a second edge 52. The wheel20 has a rotational axis 54 about which the wheel 20 is symmetrical. Thecylindrical polar coordinate system 32 is positioned so that thecylindrical axis 34 is oriented parallel to, and extends along, therotational axis 54. Furthermore, the origin of the cylindrical polarcoordinate system 32 is positioned half way between the first circularsurface 32 and the second circular surface 44.

The first circular surface 42 has a circular shape and is orientedparallel to the plane defined by the polar axis 36 and the azimuthalaxis 38. Similarly, the second circular surface 44 has a circular shapeand is oriented parallel to the plane defined by the polar axis 36 andthe azimuthal axis 38. Consequently, the second circular surface 44 isoriented parallel to the first circular surface 42. The first and secondcircular surfaces 42, 44 may provide the hub of the wheel 20 into whicha shaft, coupled to one of the actuators 16, may be inserted. The firstand second circular surfaces 42, 44 may be planar (as illustrated inFIG. 2), or may be non-planar (as illustrated in FIG. 3).

The first rim surface 46 extends from the first circular surface 42 atthe first edge 50 and defines at least a part of the circumference 40 ofthe wheel 20. A gradient of the first rim surface 46 (relative to thecylindrical axis 34) has a radial component (in other words, the firstrim surface 46 extends in the cylindrical axis 34, the polar axis 36,and the azimuthal axis 38). Consequently, the first rim surface 46 has atapered or chamfered profile relative to the first circular surface 42.In some examples, the first rim surface 46 may have a constant gradientalong the cylindrical axis 34 (as illustrated in FIG. 2) between thefirst edge 50 and the opposite end of the first rim surface 46. In otherexamples, the first rim surface 46 may have a varying gradient along thecylindrical axis 34 (for example, the magnitude of the gradient of thefirst rim surface 46 may decrease in the positive direction of thecylindrical axis 34).

The second rim surface 48 extends from the second circular surface 44 ata second edge 52 and towards the first rim surface 46. The second rimsurface 48 defines at least a part of the circumference 40 of the wheel20. A gradient of the second rim surface 48 (relative to the cylindricalaxis 34) has a radial component (in other words, the second rim surface48 extends in the cylindrical axis 34, the polar axis 36 and theazimuthal axis 38). Therefore, the second rim surface 48 has a taperedor chamfered profile relative to the second circular surface 44. In someexamples, the second rim surface 48 may have a constant gradient alongthe cylindrical axis 34 (as illustrated in FIG. 2) between the secondedge 52 and the opposite end of the second rim surface 48. In otherexamples, the second rim surface 48 may have a varying gradient alongthe cylindrical axis 34 (for example, the magnitude of the gradient ofthe second rim surface 48 may increase in the positive direction of thecylindrical axis 34).

The first edge 50 defines a curved surface between the first circularsurface 42 and the first rim surface 46. The magnitude of the gradientof the first edge 50 (relative to the cylindrical axis 34) may decreasein the positive direction of the cylindrical axis 34 as illustrated inFIG. 2. The second edge 52 defines a curved surface between the secondcircular surface 44 and the second rim surface 48. The magnitude of thegradient of the second edge 52 (relative to the cylindrical axis 34) mayincrease in the positive direction of the cylindrical axis 34.Consequently, the first edge 50 and the second edge 52 each define afillet radius.

The first rim surface 46 has a depth of D1 along the polar axis. Thesecond rim surface 48 may have the same depth along the polar axis 36 asthe first rim surface 46 (that is, a depth of D1 as illustrated in FIG.2), or may have a different depth to the first rim surface 46. The firstedge 50 has a depth of D2 along the polar axis 36. The second edge 52may have the same depth along the polar axis 36 as the first edge 50(that is, a depth of D2 as illustrated in FIG. 2). The depths of thefirst and second rim surfaces 46, 48 (that is, the depth D1) may be thesame as the depths of the first and second edges 50, 52 (that is, thedepth D2). In other examples, the depths (D1) of the first and secondrim surfaces 46, 48 may be different to the depths (D2) of the first andsecond edges 50, 52.

The first rim surface 46 and the second rim surface 48 may be directlyjoined to one another with no intervening surfaces there between asillustrated in FIG. 2. Consequently, the first rim surface 46 and thesecond rim surface 48 may define a vertex where they join one another.In other examples, the first rim surface 46 and the second rim surface48 may be indirectly joined to one another where one or more interveningsurfaces join the first rim surface 46 and the second rim surface 48 toone another.

The first rim surface 46 and the second rim surface 48 may be joined toone another (either directly or indirectly) at a location equidistantbetween the first circular surface 42 and the second circular surface 44as illustrated in FIG. 2. In other examples, the first rim surface 46and the second rim surface 48 may be joined to one another (eitherdirectly or indirectly) at a location that is either closer to the firstcircular surface 42 or closer to the second circular surface 44.

The first rim surface 46, the second rim surface 48, the first edge 50and the second edge 52 may be arranged to receive an abrasive belt(illustrated in FIG. 8 for example) for linishing the object 12. Inother examples, the first rim surface 46, the second rim surface 48, thefirst edge 50 and the second edge 52 may comprise an abrasive materialfor directly polishing or grinding the object 12.

The wheel 20 may include a hub (formed from the first and secondcircular surfaces 42, 44) comprising aluminium and a perimeter section(formed from the first rim surface 46, the second rim surface 48, thefirst edge 50, and the second edge 52) comprising rubber. In someexamples, the rubber may have a hardness of ‘Shore A—55 DURO’ and have aYoung's modulus of 1.9 MPa. In one example, the Young's modulus of therubber may be 1.919 MPa.

FIG. 3 illustrates a perspective view of another wheel 201 according tovarious examples. The wheel 201 is similar to the wheel 20 and where thefeatures are similar, the same reference numerals are used.

The wheel 201 differs in that the first rim surface 46, the second rimsurface 48, the first edge 50 and the second edge 52 define a pluralityof grooves 56 that may advantageously increase the coefficient offriction of the circumference 40 of the wheel 201. The plurality ofgrooves 56 extend radially inwardly from the circumference 40 (that is,they extend from the circumference 40 and towards the origin of thecylindrical polar coordinate system 32 along the polar axis 36).

The wheel 201 also defines an aperture 58 for receiving a shaft coupledto one of the actuators 16. Additionally, the first and second circularsurfaces 42, 44 are non-planar such that radially inner sections of thefirst and second circular surfaces 42, 44 are positioned closer together(along the cylindrical axis 34) than radially outer sections of thefirst and second circular surfaces 42, 44.

FIG. 4 illustrates a flow diagram of a method of machining an object 12including one or more filleted parts according to various examples.

At block 60, the method may include receiving information on theposition of the object 12. The controller 14 may control the one or moresensors 18 to determine the position of the surfaces of the object 12and may then receive positional information on the sensed surfaces. Forexample, where the object 12 includes one or more filleted parts (thatis, the object 12 has one or more parts having a concave surface), thecontroller 14 may control the sensors 18 to determine the position andorientation of those concave surfaces.

At block 62, the method may include determining a machining path usingthe information received at block 60. For example, the controller 14 mayuse the positional information received at block 60 to determine thepath along which the wheel 20, 201 is to be moved to machine the one ormore concave surfaces of the object 12.

At block 64, the method includes controlling orientation of the wheel20, 201 and/or the object 12 so that the cylindrical axis 34 of thewheel 20, 201 is orthogonal to the longitudinal axis of the filletedpart during machining of the object 12. The controller 14 may controlone or more of the actuators 16 to rotate the wheel 20, 201 and/or theobject 12 so that the cylindrical axis 34 of the wheel 20, 201 isorthogonal to the longitudinal axis of the filleted part.

FIG. 5 illustrates a perspective view of a fan blade 12 to be machinedby the wheel 20, 201 according to various examples.

The fan blade 12 includes a root portion 66 and an aerofoil portion 68that define a filleted part 70 there between. The filleted part 70 has alongitudinal axis 72 and the aerofoil portion 68 has a longitudinal axis74. The longitudinal axis 72 of the filleted part 70 is orthogonal tothe longitudinal axis 74 of the aerofoil portion 68.

The apparatus 10 includes an abrasive belt 76 that extends around thewheel 20, 201 and forms an endless loop. It should be appreciated thatin other examples, the apparatus 10 may not include the abrasive belt 76and instead, the wheel 20, 201 may comprise an abrasive material fordirectly machining the fan blade 12.

As illustrated in FIG. 5, the wheel 20, 201 has been re-oriented by theactuators 16 (which comprise a robotic arm in this example) so that thecylindrical axis 34 of the wheel 20, 201 is orthogonal to thelongitudinal axis 72 of the filleted part 70. In other words, the wheel20, 201 has been re-oriented so that the circumference 40 of the wheel20, 201 is parallel to the longitudinal axis 72 of the filleted part 70.

At block 78, the method includes controlling one or more of theactuators 16 to rotate the wheel 20, 201 about the axis 54 in thedirection of the azimuthal axis 38 (either the positive or the negativedirection of the azimuthal axis 38) to machine the fan blade 12. Forexample, the controller 14 may control the actuators 16 to rotate thewheel 20, 201 and to move the wheel 20, 201 into contact with thefilleted part 70 of the fan blade 12 as illustrated in FIG. 6. Thecontroller 14 may then control the actuators 16 to move the wheel 20,201 along the longitudinal axis 72 of the filleted part 70 to machinealong the length of the filleted part 70.

Once machining is completed, the method may end at block 80.Alternatively, the method may return to block 60 and the controller 14may control the one or more sensors 18 to sense the position of thesurfaces of the fan blade 12 to determine whether further machining ofthe fan blade 12 is required. Where the controller 14 determines thatfurther machining is required, the method proceeds through blocks 62, 64and 78.

FIG. 7 illustrates a graph 82 of pressure applied by two differentwheels along a radial length of the filleted part 70 of the fan blade 12illustrated in FIG. 6. In more detail, the graph 82 includes ahorizontal axis 84 for the radial position (in millimetres) along thesurface of the filleted part 70, and a vertical axis 86 for the pressure(in kilograms per square millimetre) applied by the wheel 20, 201. Thegraph 82 also includes a dotted line 88 for the pressure applied by afirst wheel 20, 201, and a solid line 90 for the pressure applied by asecond wheel 20, 201.

The first wheel 20, 201 has a depth D1 of two millimetres and a depth D2of two millimetres. The second wheel 20, 201 has a depth D1 of fourmillimetres and a depth D2 of two millimetres. As illustrated in FIG. 7,the first wheel 20, 201 has a generally flat pressure profile with apeak of approximately 0.29 kilograms per square millimetre at the radialdistance of 5 millimetres. The second wheel 20, 201 has a more unevenpressure profile with a peak of approximately 0.55 kilograms per squaremillimetre at the radial distance of 6 millimetres. The second wheel 20,201 may be preferred for machining where higher pressure and materialremoval are desired. The first wheel 20, 201 may be preferred formachining where lower pressure and material removal are desired.

It should be appreciated that the values of D1 and D2 mentioned aboveare provided as an example only and that D1 and D2 may have differentvalues in other examples.

FIG. 8 illustrates a perspective view of the fan blade 12 illustrated inFIGS. 5 and 6 and the distribution of pressure 92 applied by the secondwheel 20, 201 mentioned in the preceding paragraphs as the second wheel20, 201 is moved along the longitudinal axis 72. The distribution ofpressure 92 has an elliptical shape and the pressure increases towardsthe centre of the ellipse (illustrated in FIG. 8 where a lighter shadeof grey indicates a higher pressure applied by the second wheel 20, 201on the filleted part 70).

The apparatus 10 may provide several advantages. First, the profile ofthe circumference 40 of the wheel 20, 201 (in particular, the chamferedand fillet radii profile) may enable the wheel 20, 201 to access concavesurfaces of an object 12 to machine such surfaces. Consequently, theapparatus 10 and method described in the preceding paragraphs may finishthe object 12 to a higher level of quality.

Second, the profile of the circumference 40 of the wheel 20, 201 mayenable machining of concave surfaces to be computer controlled. This mayreduce industrial injuries caused by machining and may also reduce therisk of a fire caused by dust from machining (since the machining may beperformed in a confined environment where dust is thoroughly extracted).

Third, the wheel 20, 201 may be manufactured to be compatible withexisting robotic apparatus and may consequently be relativelyinexpensive to implement. For example, the aperture 58 and the first andsecond circular surfaces 42, 44 may be manufactured to fit one or moreexisting robotic apparatus.

Fourth, the fillet edges 50, 52 in the wheel 20, 201 may reduce thepossibility of ‘under-cutting’ (the wheel digging into the surface ofthe object 12) while the wheel moves up and down along the concavefeature (arrow 94 in FIG. 6 for example represents motion along theconcave feature).

It will be understood that the invention is not limited to theembodiments above-described and various modifications and improvementscan be made without departing from the concepts described herein. Forexample, only one of the edges 50, 52 may define a curved surface. Inother words, only one of the edges 50, 52 may define a fillet radius andthe other one of the edges 50, 52 may define a vertex.

Except where mutually exclusive, any of the features may be employedseparately or in combination with any other features and the disclosureextends to and includes all combinations and sub-combinations of one ormore features described herein.

What is claimed is:
 1. Apparatus for machining an object, the apparatuscomprising: a wheel having a circumference, the wheel including: a firstcircular surface; a second circular surface oriented parallel to thefirst circular surface; a first rim surface extending from the firstcircular surface at a first edge and defining at least a part of thecircumference of the wheel, a gradient of the first rim surface having aradial component; and a second rim surface extending from the secondcircular surface at a second edge and towards the first rim surface, thesecond rim surface defining at least a part of the circumference of thewheel, a gradient of the second rim surface having a radial component,the first edge defining a curved surface between the first circularsurface and the first rim surface, and the second edge defining a curvedsurface between the second circular surface and the second rim surface.2. Apparatus as claimed in claim 1, wherein the first rim surface andthe second rim surface are directly joined to one another with nointervening surfaces there between.
 3. Apparatus as claimed in claim 2,wherein the first rim surface and the second rim surface abut oneanother at a location equidistant between the first circular surface andthe second circular surface.
 4. Apparatus as claimed in claim 1, whereinthe first rim surface, the second rim surface, the first edge and thesecond edge are arranged to receive an abrasive belt for linishing theobject.
 5. Apparatus as claimed in claim 1, wherein the first rimsurface, the second rim surface, the first edge and the second edgecomprise an abrasive material for polishing or grinding the object. 6.Apparatus as claimed in claim 1, wherein the first rim surface, thesecond rim surface, the first edge and the second edge define aplurality of grooves.
 7. Apparatus as claimed in claim 1, wherein theobject includes a filleted part extending along a longitudinal axis, theapparatus further comprising a controller configured to controlorientation of the wheel and/or the object so that a cylindrical axis ofthe wheel is orthogonal to the longitudinal axis of the filleted partduring machining of the object.
 8. Apparatus as claimed in claim 1,wherein the wheel includes: a hub comprising aluminium; and a perimetersection comprising rubber.
 9. A method of controlling apparatus asclaimed in claim 1 to machine an object including a filleted partextending along a longitudinal axis, the method comprising: controllingorientation of the wheel and/or the object so that a cylindrical axis ofthe wheel is orthogonal to the longitudinal axis of the filleted partduring machining of the object.
 10. A non-transitory computer readablestorage medium comprising computer readable instructions that, when readby a computer, cause performance of the method as claimed in claim 9.